Makes display roots be destroyed by client

services/ui/public/cpp/window_manager_delegate.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SERVICES_UI_PUBLIC_CPP_WINDOW_MANAGER_DELEGATE_H_
 #define SERVICES_UI_PUBLIC_CPP_WINDOW_MANAGER_DELEGATE_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 88 matching lines @@
   // windows owned by the window manager in which the client is embedded.
   virtual void OnWmClientJankinessChanged(
       const std::set<Window*>& client_windows,
       bool janky) = 0;
 
   // Called when a display is added. |window| is the root of the window tree for
   // the specified display.
   virtual void OnWmNewDisplay(Window* window,
                               const display::Display& display) = 0;
 
+  // Called when a display is removed. |window| is the root of the display.
+  virtual void OnWmDisplayRemoved(Window* window) = 0;
+
   virtual mojom::EventResult OnAccelerator(uint32_t id, const ui::Event& event);
 
   virtual void OnWmPerformMoveLoop(
       Window* window,
       ui::mojom::MoveLoopSource source,
       const gfx::Point& cursor_location,
       const base::Callback<void(bool)>& on_done) = 0;
 
   virtual void OnWmCancelMoveLoop(Window* window) = 0;
 
  protected:
   virtual ~WindowManagerDelegate() {}
 };
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_PUBLIC_CPP_WINDOW_MANAGER_DELEGATE_H_